1. Technical Field
Example embodiments relate generally to semiconductor integrated circuits, and more particularly to a memory device performing a hammer refresh operation and a memory system including the memory device.
2. Discussion of the Related Art
Semiconductor memory devices for storing data may be classified into volatile memory devices and non-volatile memory devices. Volatile memory devices, such as dynamic random access memory (DRAM) devices, may be configured to store data by charging or discharging capacitors in memory cells, and lose the stored data when power is off. Non-volatile memory devices, such as flash memory devices, may maintain stored data even when power is off. Volatile memory devices are widely used as main memories of various apparatuses, and non-volatile memory devices are widely used for storing program code and/or data in various electronic devices, such as computers, mobile devices, etc.
In volatile memory devices, cell charges stored in a memory cell may be lost by a leakage current. In addition, when a wordline is transitioned frequently between an active state and a precharged state (i.e., when the wordline has been accessed intensively or frequently), an affected memory cell connected to a wordline that is adjacent to the frequently accessed wordline may lose stored charges. Charges stored in a memory cell may be maintained by recharging before data is lost by leakage of cell charges. Such recharge of cell charges is referred to as a refresh operation, and a refresh operation may be performed repeatedly before cell charges are significantly lost.